Add missing semicolumns in engine.js
Add optional extra args to JS Engine.startGame
Remove loader.js, explicit noExitRuntime.
Also add onExit callback (undocumented in emscripten)
- Refactored the Engine code, splitted across files.
- Use MODULARIZE option to build emscripten code into it's own closure.
- Enable lto support (saves ~2MiB in release).
- Enable optional closure compiler pass for JS and generated code.
- Enable optional pthreads support.
- Can now build with tools=yes (not much to see yet).
- Dropped some deprecated code for older toolchains.
